The object of the invention is a method of controlling the thermal balance of the reaction shaft of a suspension smelting furnace.
Another object of the invention is a concentrate burner for feeding a reaction gas and pulverous solid matter into the reaction shaft of the 10 suspension smelting furnace.
The invention relates to the method that takes place in the suspension smelting furnace, such as a flash smelting furnace, and to the concentrate burner for feeding the reaction gas and pulverous solid matter into the reaction shaft of the suspension smelting furnace, such as flash the smelting furnace.
The flash smelting furnace comprises three main parts: a reaction shaft, a lower furnace and an uptake. In the flash smelting process, the pulverous solid matter that comprises a sulphidic concentrate, slag forming agent and other pulverous components, is mixed with the reaction gas by means of the concentrate burner in the upper part of the reaction shaft. The reaction gas can be air, oxygen or oxygen-enriched air. The concentrate burner comprises normally a feeder pipe for feeding the pulverous solid matter into the reaction shaft, where the orifice of the feeder pipe opens to the reaction shaft. The concentrate burner further comprises normally a dispersing device, which is arranged concentrically inside the feeder pipe and which extends to a distance from the orifices of the feeder pipe inside the reaction shaft and which comprises dispersion gas openings for directing a dispersion gas to the pulverous solid matter that flows around the dispersing device. The concentrate burner further comprises normally a gas supply device for feeding the reaction gas into the reaction shaft, the gas supply device opening to the reaction shaft through an annular discharge orifice that surrounds the feeder pipe concentrically for mixing the said reaction gas that discharges from the annular discharge orifice with the pulverous solid matter, which discharges from the middle of the feeder pipe and which is directed to the side by means of the dispersion gas. The flash smelting process comprises a stage, wherein the pulverous solid matter is fed into the reaction shaft through the orifice of the feeder pipe of the concentrate burner. The flash smelting process further comprises a stage, wherein the dispersion gas is fed into the reaction shaft through the dispersion gas orifices of the dispersing device of the concentrate burner for directing the dispersion gas to the pulverous solid matter that flows around the dispersing device, and a stage, wherein the reaction gas is fed into the reaction shaft through the annular discharge orifice of the gas supply device of the concentrate burner for mixing the reaction gas with the solid matter, which discharges from the middle of the feeder pipe and which is directed to the side by means of the dispersion gas.
In most cases, the energy needed for the melting is obtained from the mixture itself, when the components of the mixture that is fed into the reaction shaft, the powdery solid matter and the reaction gas react with each other. However, there are raw materials, which do not produce enough energy when reacting together and which, for a sufficient melting, require that fuel gas is also fed into the reaction shaft to produce energy for the melting.
At present, there are various known alternatives of correcting upwards the thermal balance of the reaction shaft of the suspension smelting furnace, i.e., raising the temperature of the reaction shaft of the suspension smelting furnace to prevent the reaction shaft of the suspension smelting furnace from cooling. There are not many known ways of correcting downwards the thermal balance of the reaction shaft of the suspension smelting furnace, i.e., lowering the temperature of the reaction shaft of the suspension smelting furnace. One known method is to decrease the feed, i.e., to feed a lesser amount of concentrate and reaction gas into the reaction shaft, for example. For the sake of productivity, it would also be good to succeed in decreasing the thermal balance without decreasing the feed.
The patent specification WO 2009/030808 presents a concentrate burner.